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diff --git a/testing/mozbase/mozdebug/mozdebug/mozdebug.py b/testing/mozbase/mozdebug/mozdebug/mozdebug.py
new file mode 100755
index 0000000000..19f80f8d6a
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+++ b/testing/mozbase/mozdebug/mozdebug/mozdebug.py
@@ -0,0 +1,315 @@
+#!/usr/bin/env python
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import json
+import os
+import sys
+from collections import namedtuple
+from distutils.spawn import find_executable
+from subprocess import check_output
+
+import mozinfo
+
+__all__ = [
+    "get_debugger_info",
+    "get_default_debugger_name",
+    "DebuggerSearch",
+    "get_default_valgrind_args",
+    "DebuggerInfo",
+]
+
+"""
+Map of debugging programs to information about them, like default arguments
+and whether or not they are interactive.
+
+To add support for a new debugger, simply add the relative entry in
+_DEBUGGER_INFO and optionally update the _DEBUGGER_PRIORITIES.
+"""
+_DEBUGGER_INFO = {
+    # gdb requires that you supply the '--args' flag in order to pass arguments
+    # after the executable name to the executable.
+    "gdb": {"interactive": True, "args": ["-q", "--args"]},
+    "cgdb": {"interactive": True, "args": ["-q", "--args"]},
+    "rust-gdb": {"interactive": True, "args": ["-q", "--args"]},
+    "lldb": {"interactive": True, "args": ["--"], "requiresEscapedArgs": True},
+    # Visual Studio Debugger Support.
+    "devenv.exe": {"interactive": True, "args": ["-debugexe"]},
+    # Visual C++ Express Debugger Support.
+    "wdexpress.exe": {"interactive": True, "args": ["-debugexe"]},
+    # Windows Development Kit super-debugger.
+    "windbg.exe": {
+        "interactive": True,
+    },
+}
+
+# Maps each OS platform to the preferred debugger programs found in _DEBUGGER_INFO.
+_DEBUGGER_PRIORITIES = {
+    "win": ["devenv.exe", "wdexpress.exe"],
+    "linux": ["gdb", "cgdb", "lldb"],
+    "mac": ["lldb", "gdb"],
+    "android": ["lldb"],
+    "unknown": ["gdb"],
+}
+
+
+DebuggerInfo = namedtuple(
+    "DebuggerInfo", ["path", "interactive", "args", "requiresEscapedArgs"]
+)
+
+
+def _windbg_installation_paths():
+    programFilesSuffixes = ["", " (x86)"]
+    programFiles = "C:/Program Files"
+    # Try the most recent versions first.
+    windowsKitsVersions = ["10", "8.1", "8"]
+
+    for suffix in programFilesSuffixes:
+        windowsKitsPrefix = os.path.join(programFiles + suffix, "Windows Kits")
+        for version in windowsKitsVersions:
+            yield os.path.join(
+                windowsKitsPrefix, version, "Debuggers", "x64", "windbg.exe"
+            )
+
+
+def _vswhere_path():
+    try:
+        import buildconfig
+
+        path = os.path.join(buildconfig.topsrcdir, "build", "win32", "vswhere.exe")
+        if os.path.isfile(path):
+            return path
+    except ImportError:
+        pass
+    # Hope it's available on PATH!
+    return "vswhere.exe"
+
+
+def get_debugger_path(debugger):
+    """
+    Get the full path of the debugger.
+
+    :param debugger: The name of the debugger.
+    """
+
+    if mozinfo.os == "mac" and debugger == "lldb":
+        # On newer OSX versions System Integrity Protections prevents us from
+        # setting certain env vars for a process such as DYLD_LIBRARY_PATH if
+        # it's in a protected directory such as /usr/bin. This is the case for
+        # lldb, so we try to find an instance under the Xcode install instead.
+
+        # Attempt to use the xcrun util to find the path.
+        try:
+            path = check_output(
+                ["xcrun", "--find", "lldb"], universal_newlines=True
+            ).strip()
+            if path:
+                return path
+        except Exception:
+            # Just default to find_executable instead.
+            pass
+
+    if mozinfo.os == "win" and debugger == "devenv.exe":
+        # Attempt to use vswhere to find the path.
+        try:
+            encoding = "mbcs" if sys.platform == "win32" else "utf-8"
+            vswhere = _vswhere_path()
+            vsinfo = check_output([vswhere, "-format", "json", "-latest"])
+            vsinfo = json.loads(vsinfo.decode(encoding, "replace"))
+            return os.path.join(
+                vsinfo[0]["installationPath"], "Common7", "IDE", "devenv.exe"
+            )
+        except Exception:
+            # Just default to find_executable instead.
+            pass
+
+    return find_executable(debugger)
+
+
+def get_debugger_info(debugger, debuggerArgs=None, debuggerInteractive=False):
+    """
+    Get the information about the requested debugger.
+
+    Returns a dictionary containing the |path| of the debugger executable,
+    if it will run in |interactive| mode, its arguments and whether it needs
+    to escape arguments it passes to the debugged program (|requiresEscapedArgs|).
+    If the debugger cannot be found in the system, returns |None|.
+
+    :param debugger: The name of the debugger.
+    :param debuggerArgs: If specified, it's the arguments to pass to the debugger,
+    as a string. Any debugger-specific separator arguments are appended after these
+    arguments.
+    :param debuggerInteractive: If specified, forces the debugger to be interactive.
+    """
+
+    debuggerPath = None
+
+    if debugger:
+        # Append '.exe' to the debugger on Windows if it's not present,
+        # so things like '--debugger=devenv' work.
+        if os.name == "nt" and not debugger.lower().endswith(".exe"):
+            debugger += ".exe"
+
+        debuggerPath = get_debugger_path(debugger)
+
+    if not debuggerPath:
+        # windbg is not installed with the standard set of tools, and it's
+        # entirely possible that the user hasn't added the install location to
+        # PATH, so we have to be a little more clever than normal to locate it.
+        # Just try to look for it in the standard installed location(s).
+        if debugger == "windbg.exe":
+            for candidate in _windbg_installation_paths():
+                if os.path.exists(candidate):
+                    debuggerPath = candidate
+                    break
+        else:
+            if os.path.exists(debugger):
+                debuggerPath = debugger
+
+    if not debuggerPath:
+        print("Error: Could not find debugger %s." % debugger)
+        print("Is it installed? Is it in your PATH?")
+        return None
+
+    debuggerName = os.path.basename(debuggerPath).lower()
+
+    def get_debugger_info(type, default):
+        if debuggerName in _DEBUGGER_INFO and type in _DEBUGGER_INFO[debuggerName]:
+            return _DEBUGGER_INFO[debuggerName][type]
+        return default
+
+    # Define a namedtuple to access the debugger information from the outside world.
+    debugger_arguments = []
+
+    if debuggerArgs:
+        # Append the provided debugger arguments at the end of the arguments list.
+        debugger_arguments += debuggerArgs.split()
+
+    debugger_arguments += get_debugger_info("args", [])
+
+    # Override the default debugger interactive mode if needed.
+    debugger_interactive = get_debugger_info("interactive", False)
+    if debuggerInteractive:
+        debugger_interactive = debuggerInteractive
+
+    d = DebuggerInfo(
+        debuggerPath,
+        debugger_interactive,
+        debugger_arguments,
+        get_debugger_info("requiresEscapedArgs", False),
+    )
+
+    return d
+
+
+# Defines the search policies to use in get_default_debugger_name.
+
+
+class DebuggerSearch:
+    OnlyFirst = 1
+    KeepLooking = 2
+
+
+def get_default_debugger_name(search=DebuggerSearch.OnlyFirst):
+    """
+    Get the debugger name for the default debugger on current platform.
+
+    :param search: If specified, stops looking for the debugger if the
+     default one is not found (|DebuggerSearch.OnlyFirst|) or keeps
+     looking for other compatible debuggers (|DebuggerSearch.KeepLooking|).
+    """
+
+    mozinfo.find_and_update_from_json()
+    os = mozinfo.info["os"]
+
+    # Find out which debuggers are preferred for use on this platform.
+    debuggerPriorities = _DEBUGGER_PRIORITIES[
+        os if os in _DEBUGGER_PRIORITIES else "unknown"
+    ]
+
+    # Finally get the debugger information.
+    for debuggerName in debuggerPriorities:
+        debuggerPath = get_debugger_path(debuggerName)
+        if debuggerPath:
+            return debuggerName
+        elif not search == DebuggerSearch.KeepLooking:
+            return None
+
+    return None
+
+
+# Defines default values for Valgrind flags.
+#
+# --smc-check=all-non-file is required to deal with code generation and
+#   patching by the various JITS.  Note that this is only necessary on
+#   x86 and x86_64, but not on ARM.  This flag is only necessary for
+#   Valgrind versions prior to 3.11.
+#
+# --vex-iropt-register-updates=allregs-at-mem-access is required so that
+#   Valgrind generates correct register values whenever there is a
+#   segfault that is caught and handled.  In particular OdinMonkey
+#   requires this.  More recent Valgrinds (3.11 and later) provide
+#   --px-default=allregs-at-mem-access and
+#   --px-file-backed=unwindregs-at-mem-access
+#   which provide a significantly cheaper alternative, by restricting the
+#   precise exception behaviour to JIT generated code only.
+#
+# --trace-children=yes is required to get Valgrind to follow into
+#   content and other child processes.  The resulting output can be
+#   difficult to make sense of, and --child-silent-after-fork=yes
+#   helps by causing Valgrind to be silent for the child in the period
+#   after fork() but before its subsequent exec().
+#
+# --trace-children-skip lists processes that we are not interested
+#   in tracing into.
+#
+# --leak-check=full requests full stack traces for all leaked blocks
+#   detected at process exit.
+#
+# --show-possibly-lost=no requests blocks for which only an interior
+#   pointer was found to be considered not leaked.
+#
+#
+# TODO: pass in the user supplied args for V (--valgrind-args=) and
+# use this to detect if a different tool has been selected.  If so
+# adjust tool-specific args appropriately.
+#
+# TODO: pass in the path to the Valgrind to be used (--valgrind=), and
+# check what flags it accepts.  Possible args that might be beneficial:
+#
+# --num-transtab-sectors=24   [reduces re-jitting overheads in long runs]
+# --px-default=allregs-at-mem-access
+# --px-file-backed=unwindregs-at-mem-access
+#                             [these reduce PX overheads as described above]
+#
+
+
+def get_default_valgrind_args():
+    return [
+        "--fair-sched=yes",
+        "--smc-check=all-non-file",
+        "--vex-iropt-register-updates=allregs-at-mem-access",
+        "--trace-children=yes",
+        "--child-silent-after-fork=yes",
+        (
+            "--trace-children-skip="
+            + "/usr/bin/hg,/bin/rm,*/bin/certutil,*/bin/pk12util,"
+            + "*/bin/ssltunnel,*/bin/uname,*/bin/which,*/bin/ps,"
+            + "*/bin/grep,*/bin/java,*/bin/lsb_release"
+        ),
+    ] + get_default_valgrind_tool_specific_args()
+
+
+# The default tool is Memcheck.  Feeding these arguments to a different
+# Valgrind tool will cause it to fail at startup, so don't do that!
+
+
+def get_default_valgrind_tool_specific_args():
+    return [
+        "--partial-loads-ok=yes",
+        "--leak-check=summary",
+        "--show-possibly-lost=no",
+        "--show-mismatched-frees=no",
+    ]